Impact of urban vegetation on thermal comfort in the tropical coastal city of Fortaleza

Abstract

The thermal comfort in cities is closely dependent on the urban physiography characteristics. In addition to the urban heat island effect, the predicted increase in air temperature as a result of climate change leads to the importance of defining and implementing effective adaptation plans to make cities more pleasant to live in. In this context, we focus on understanding how climate and urban physiography affect human thermal conform, to provide useful information towards a more sustainable urban planning in a climate change context in tropical cities.In this study, the dynamical downscaling up to 1km resolution over Fortaleza city was performed with the convective-permitting regional model HARMONIE-Climate (HCLIMcy38), forced by ERA5 boundary conditions. HCLIM embraces the land surface model SURFEX to simulate urban surface fluxes. The urban physiography is described by the Local Climate Zones and ECOCLIMAP databases. HCLIM modelling outcomes as well as meteorological data from five recent-past years representing assorted climate conditions are used to study different intra-urban microclimates based on different land uses (e.g. parks and residential areas). Additionally, air temperature and relative humidity observations from a measurement campaign with 14 low-cost sensors spread through the city complement the analysis with more detailed local information. Three different environments within the urban area of Fortaleza are taken as example: built-up area, mainly compact high-rise; Urban forest and Lake. The results show that during the wet season, the built-up area is under moderate heat stress during all day, while both urban forest and lake vary from moderate at night to strong heat stress during the sun-light hours. On the other hand, during the dry season, all environments present a similar curve, with thermal comfort indexes varying from moderate to strong heat stress during sun-light hours and no heat stress in the night. The analysis thermal comfort indexes can provide valuable information to urban planners on how people perceive the heat, on where to place new residential areas and how to plan new or recover existent parks in tropical cities.